I recently had a problem with an Exchange Online tenant. There was an external mail contact which was previously synchronised from Active Directory to Exchange Online. So I had deleted the on-premise active directory mail contact but it still existed in Exchange Online. When I tried to delete the contact it gave the following errror message.


The action ‘Remove-MailContact’, ‘Identity’, can’t be performed on the object ‘Desmond Miles’ because the object is being synchronized from your on-premises organization. This action should be performed on the object in your on-premises organization.


To trouble shoot this issue you can do a couple of things to ensure the external contact does not exist in your on premise Active Directory.

Connect to your Exchange Online Tenant:

$UserCredential = Get-Credential
$Session = New-PSSession -ConfigurationName Microsoft.Exchange -ConnectionUri https://outlook.office365.com/powershell-liveid/ -Credential $UserCredential -Authentication Basic -AllowRedirection
Import-PSSession $Session
  1. Perform a custom search in ADUC: Search Syntax : proxyaddresses=SMTP:desmond.miles@contoso.com
  2. Search the WAAD Mettaverse
  3. Run this command on the Exchange Onpremise management shell
    remove-mailcontact desmond.miles@contoso.com
So if after running all of the above steps you cannot find the external contact which is causing the issues. You do the following.
In Exchange Online Run this command :
get-mailcontact sean.ofarrell@contos.com | fl

Take note of the attribute value: ExternalDirectoryObjectId
In this example the externaldirectoryobjectid is 2cb3d9c7-cb29-439f-8174-6c80dd9fe6e8
Then connect to Windows Azure Ad via Powershell and run this command:

get-msolcontact -objectid 2cb3d9c7-cb29-439f-8174-6c80dd9fe6e8 | remove-msolcontact


Problem solved. Now run a delta sync on your WAAD server and everything will work fine.





Photo by Neko Tai on Unsplash